1. Field of the Invention
The present invention relates generally to optical network devices, and more particularly to a network device of an optical network terminal (ONT) and a method of adjusting power of optical signals.
2. Description of the Related Art
For the development of transmission technology through network, optical transmission is replacing the traditional electrical transmission. Gigabits passive optical network (GPON) has been widely applied in network structures to provide high speed transmission and to broaden the bandwidth.
The GPON system includes an optical line terminal (OLT) at the service provider's central office (CO) and a plurality of optical network terminals (ONTs) near end users. OLT transmits downstream and upstream signals between CO and ONTs.
However, the distance between each ONT and the OLT depends, and ONT always transmits optical signals with fixed transmission power. Therefore, for those ONTs set at far, the transmission power may be insufficient, so that the transmission may be incomplete or erroneous. On the contrary, for the transmission between the OLT and those ONTs set near, the transmission power may be too high to cause waste of energy, shorter lifespan of transmission units, and higher cost for maintenance.
The drawbacks described above are unavoidable, as long as the distances between the ONTs and the OLT are different.